The application of images to bars of soap is desirable in a number of situations. Hotels, for example, often offer their guests individual soap bars bearing the hotel name or trademark. Soap manufacturers like to affix names or trademarks to their soap products to promote brand identification. In other instances, soap with purely decorative images is desired. No matter what the reason for applying a decorative or information-carrying image to a bar of soap, it is universally desired that the image remain visible on the soap until the soap is substantially completely used tip. The three-dimensional lettering, designs and images often stamped on soap bars quickly wear down as the soap is used and disappear long before the soap is used up. It is highly desired by soap manufacturers, hotels and others who customarily use such information-carrying soaps to have a labeled soap that continues to impart the desired message to the user as long as the soap is usable. It is also highly desired that such a labeled soap be available at a cost comparable to that of producing soap automatically stamped with three dimensional designs and information.
The prior art has proposed methods of decorating or applying information-carrying images to bars of soap. In U.S. Pat. No. 3,565,709 to Grebe, for example, an image-carrying sheet material is smoothed manually onto the face of a piece of soap which has been completely dried. The sheet material and an annular face portion of the soap are then completely covered with a continuous, transparent, waterproof and pliable layer of an organic coating material. As this method is described by Grebe, it can only be conducted manually on dry soap bars, which makes it a very costly way to apply an information-bearing label to a soap bar. Moreover, the image-bearing sheet materials disclosed by Grebe for application to soap bars tend to winkle after the coating has been applied and become detached easily from the soap so that they do not remain on the soap until it is used up.
British Patent No. 20,768 discloses a method for labeling or stamping soap with a label made of paper wherein the label is embedded in a relief or intaglio device including a raised edge around the label stamped in the soap. Although a label embossed on the soap in this manner is not easily removed at first, as the raised edge wears down, the label will separate from the soap and will not remain permanently affixed to the soap until the soap is substantially used up.
U.S. Pat. No. 4,297,228 to Kamada et al. discloses a method of making a decorated soap in which a synthetic resin layer is formed on one surface of the soap, and a printed transfer sheet containing a layer of adhesive is adhered to the resin layer. A backing film is then removed from the transfer sheet to reveal the image. Japanese Patent No. 59-208000 discloses the application of an image-carrying resin film to the face of a bar of soap with a binder and the coating of the image on the film with a plastic paint.
U.S. Pat. Nos. 1,827,549 to Villain; 1,983,002 to Reeves; 3,432,325 to Baba and 4,078,482 to Goering et al. are illustrative of other available methods for applying images to soap bars.
British Patent Application No. 2148927 discloses the application of a layer of a foil sheet material to a bar of soap, but for the express purpose of holding the soap together as it is used.
The prior art clearly fails to address the main problem encountered today in the manufacture of a labeled soap. The cost of producing soap with printed or drawn information-carrying images which remain on the soap until the soap is used up is very expensive unless the image can be affixed to each bar of soap during the continuous production of a large number of bars of soap. The soap is typically very moist and soft during continuous production, and the surface to be affixed with a label will decrease in size as the soap dries. It is not unusual for the soap to lose up to 15% of its original size during production as water evaporates. The available prior art methods of labeling soap result in the labels becoming swollen and distorted and detached from the soap because the soap is not dry. Consequently, any kind of adhesive or glue loses its ability to affix the label to the soap.
The prior art, therefore, has failed to provide a low cost, reliable method of affixing an image-bearing label to a bar of soap during soap manufacture which does not require drying of the soap so that the label remains stable, attractive and affixed to the soap for as long as the soap lasts. The prior art has further failed to provide a low cost labeled soap that substantially permanently retains its label as the soap is used up.